I have a NetGear, Inc. WNA1100 Wireless-N 150 [Atheros AR9271] wifi
adapter. It works flawlessly with kernels 3.3 (with firmware-atheros
installed), but not with kernel(s) 3.4.

I can see it with lsusb, the modules (ath, ath9k_hw, ath9k_common,
ath9k_htc) all load, iwconfig and ifconfig see wlan0 (as wireless),
but I cannot connect. It makes attempts to get an IP, but fails
without connecting. (I'm using ceni.)

Please install iw and crda, both are needed for modern wlan cards; e.g. in contrast to the deprecated iwconfig, iw can display if the router offers HT. My first suspicion would hint at the regulatory compliance arena (assuming you're using HT40+), also because because you're receiving an US country IE.

An interesting test would be to (temporarily) switch the router's wlan channel to 6.

Please install iw and crda, both are needed for modern wlan cards; e.g. in contrast to the deprecated iwconfig, iw can display if the router offers HT. My first suspicion would hint at the regulatory compliance arena (assuming you're using HT40+), also because because you're receiving an US country IE.

An interesting test would be to (temporarily) switch the router's wlan channel to 6.